Katha Upanishad Verse 2.1.10
This verse emphasizes the fundamental non-duality of existence. It asserts that the reality experienced “here” (in the physical/manifest realm) is identical to what is “there” (in the spiritual/unmanifest realm). One who falls into the trap of perceiving multiplicity and difference is caught in the cycle of birth and death, moving “from Death to Death.”
Sanskrit Verse
यदेवेह तदमुत्र यदमुत्र तदन्विह । मृत्योः स मृत्युमाप्नोति य इह नानेव पश्यति ॥ १० ॥
Transliteration
yadeveha tadamutra yadamutra tadanviha | mṛtyoḥ sa mṛtyumāpnoti ya iha nāneva paśyati || 10 ||
Translation
What indeed is here, is there; what there, that here again; from Death to Death he goes; who here sees, as if different.

Muni's Play